Today utility vehicles are powered by internal combustion engines. There is a continuing drive to reduce the emissions of such vehicles for environmental reasons. One way to reduce emissions in automobiles is to automatically switch off the engine when stationary, when in traffic for example. However, this method of operation has not been introduced in utility vehicles because repetitive stopping and starting of the engine would lead to excessive delay for the operator. For instance, the multitude of hydraulic functions need to reach working pressure before the vehicle can be operated. Each time the engine is stopped, the pressures of the accumulators, etc, in the hydraulic systems drop below working pressure. This results in long periods of idling whilst the vehicle is stationary.
Another drawback of internal combustion engines is the output noise levels. This is especially the case for agricultural tractors. In addition to the problems associated with operator comfort, noisy tractors can cause distress to cattle and other animals when operating nearby. This is quite common when supplying feed to cattle in sheds in winter months.